Fundamental contribution of beta-oxidation to polyketide mycotoxin production in planta

Mol Plant Microbe Interact. 2005 Aug;18(8):783-93. doi: 10.1094/MPMI-18-0783.


Seed contamination with polyketide mycotoxins, including aflatoxin (AF) and sterigmatocystin (ST) produced by Aspergillus spp., is an agricultural, economic, and medical issue worldwide. Acetyl-CoA, the fundamental building block of all known fungal polyketides, is generated by a large number of biochemical pathways, including beta-oxidation of fatty acids and glycolysis of sugars. We present several lines of evidence to support a major role for seed fatty acids in formation of AF and ST in A. flavus, A. parasiticus, and A. nidulans. Aspergillus strains exhibiting canonical signs of oleic acid-induced peroxisome proliferation, including increased catalase activity, beta-oxidation gene expression, and peroxisomal clustering, also exhibited a marked increase in toxin gene expression and biosynthesis. Furthermore, microscopic observations showed that the ST and AF precursor norsolorinic acid accumulated in peroxisomes of all three Aspergilli. While a peroxisomal beta-oxidation mutation eliminated oleic acid-induced increases in ST in A. nidulans, a mitochondrial beta-oxidation mutation played a larger role in eliminating ST formation on oatmeal medium and on live corn kernels, implicating a fundamental role for both peroxisomal and mitochondrial beta-oxidation in toxin production.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aflatoxins / biosynthesis*
  • Anthraquinones / metabolism
  • Aspergillus / cytology
  • Aspergillus / metabolism*
  • Fatty Acid Desaturases / genetics
  • Fatty Acid Desaturases / metabolism
  • Fatty Acids / metabolism*
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Fungal
  • Mitochondria / metabolism
  • Mutation
  • Oxidation-Reduction
  • Oxidoreductases Acting on CH-CH Group Donors / genetics
  • Oxidoreductases Acting on CH-CH Group Donors / metabolism
  • Peroxisomes / metabolism
  • Plants / metabolism*
  • Plants / microbiology*
  • Sterigmatocystin / biosynthesis*
  • Transcription, Genetic


  • Aflatoxins
  • Anthraquinones
  • Fatty Acids
  • Sterigmatocystin
  • Fatty Acid Desaturases
  • Phosphatidylcholine desaturase
  • Oxidoreductases Acting on CH-CH Group Donors
  • norsolorinic acid